It would be worth a try to take it out and fully separate the halves. Not much damage can be done at this point since it is already leaking. I would then find a plastic safe 2 part epoxy and re-seal the unit and give it a test outside of the XBox. If you do it right should be able to reuse it since it is only leaking where it joins together.

I epoxied the water block back together, but I don't trust it and I think I still have a very small leak.

I also need to replace one of the 90 degree swivel hose fittings as well so I may as well buy a water block if I can find one that will fit.

I don't like the 90 degree fittings as they reduce flow rate and at least in my experience the older ones can be problematic with the seal where the joint is that swivels, but I don't like the longer tubing runs required for straight fittings.

I'm just glad it worked. Looking at your pictures I can see why a single larger block could work but I'm not aware of anything secure enough to fit across both. Something else that came to mind as a potential future solution if it starts leaking again or you run into other issues.

GPU-210 Universal blockI'm not sure if the sizes would be right but I have the feeling that two of those GPU-210 blocks turned to face each other with a sliding connector as this one might actually work as a full replacement and also remove the need for fittings/tubing between the blocks.

The original 360/PS3 kits IIRC were actually made from the universal blocks at the time that just happened to fit and were packaged together at a discount.

Don't hold your breath for backwards compatibility both microsoft and sony said they had no intentions of doing so. Their change in the CPU architecture doesn't help matters actually makes it worse as to provide any backwards support would greatly increase the cost of the unit and they really want to push the digital downloads which doesn't require the backwards compatibility support.

For flow rates there is a magic number of return... If the flow rate is too slow the heat stays on the waterblock and heat soaks the liquid making it very inefficient. As you increase the flow rate the heat soak type effect starts to go away. However once you get beyond a certain point what happens is the opposite, the liquid is in the block for such a short duration it doesn't really get a chance to absorb the heat.

To put it in other terms you can think of a car going by and you have a paintball gun in your hands. The paint balls being "heat" the slower the car is going to more bullets you can hit it with but too slow and you will be getting paint on top of paint. Too fast and you can barley hit it.

Oh ok so the flow rate in any liquid cooled system should be adjusted to what provides the best cooling.

What I might do with my 360 is try to slow the pump down some by running it on an adjustible power supply and see if cooling efficiency improves. If it does then I'll add a resistor in series with the pump to drop its voltage to what the power supply was set to.

The liquid temperature runs about 86F normally and can jump up to 93F depending on the normal room temperature.

Much better than a stock Xbox360 where the air coming out the back of the Xbox is a steady 112F.